import java.util.Scanner;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: Lily
 * Date: 2024-10-29
 * Time: 19:58
 */
public class test_1 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        long m = 0;
        long n = in.nextLong();
        for (long i = 1; i <= n; i++) {
            long x = i * i;
            if ((x - n) >= 0) {
                m = i;
                break;
            }
        }

        long ret = 0;
        if ((m * m - n) > (n - (m - 1) * (m - 1))) {
            ret = (m - 1) * (m - 1);
        } else {
            ret = (m) * (m);
        }
        System.out.println(ret);
    }
}
